CAREER: Control of Additively Manufactured Solid Rocket Fuel Grain Geometries and Combustion Analysis

高能材料如炸药、燃料、烟火组合物或推进剂具有相对大量的储存化学能。高能推进剂经历的能量转换过程，加上气体排出，导致了一种高效的飞行器推进方法。这通常是通过点燃推进剂来实现的，推进剂是由称为颗粒的部分构成的，使其燃烧并排出气体，例如在动力飞行期间从火箭中排出的气体。目前，当三维部件由作为浆料或浆料沉积的多层材料构造时，对高能材料增材制造或3D打印的理解有限。目前的颗粒制造工艺受到颗粒形成期间含能材料的厚性质和对浇注的阻力的限制。该学院早期职业发展（CAREER）奖支持的研究旨在建立关于增材制造工艺，材料参数和零件几何形状对可打印性和燃烧效率的影响的基础知识。这项工作包括几个学科，包括燃烧，流体动力学，计算科学，材料科学，控制和推进。这项研究的结果直接涉及航空航天，航空和国防工业，并为汽车，化工，能源和医疗保健领域使用的类似材料和工艺带来额外的好处。该项目还包括一个工程教育部分，涉及对中学生的宣传，并将研究成果整合到本科课程中。增材制造提供了一种创造复杂晶粒几何形状的方法，这是目前传统制造方法无法实现的，通常涉及铸造工艺。通过增材制造生产推进剂提供了几个优点，包括创建螺旋端口、具有内部尺寸和形状变化的中心穿孔、不同材料和嵌入式组件的能力。这些优点带来了性能改进，例如提高燃烧效率，改善回归率和更好的可控性。这些高能材料的增材制造的限制因素是在用于最佳性能和制造的控制参数方面的知识差距，例如用于浆料或粘合剂转移的粘性参数、层间结合、层/表面粗糙度、材料转移期间的沉降、层组成、分辨率和空隙缺陷。该奖项支持开发制造过程的数学模型，谷物性能模拟，制造谷物的实验装置以及对制造的谷物进行测试。这项工作将测试一个假设，即可以实现一个参数公式-浆料或粘合剂转移的粘度，层/表面粗糙度，分辨率和沉降-以获得使用增材制造的发动机的最佳推进剂效率。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Energetic materials such as explosives, fuels, pyrotechnic compositions, or propellants have a relatively large amount of stored chemical energy. The energy conversion processes that energetic propellants undergo, coupled with gas expulsion, lead to a highly efficient method for vehicle propulsion. This is typically achieved by igniting the propellant, which is constructed in segments called grains, causing it to burn and expel gasses, such as those expelled from a rocket during powered flight. Presently, there is limited understanding of energetic material additive manufacturing, or 3D printing, when a three-dimensional part is constructed from multiple layers of material deposited as a slurry or paste. The current grain manufacturing processes are limited by the thick nature and resistance to pouring of the energetic materials during grain formation. The research supported by this Faculty Early Career Development (CAREER) award aims at building fundamental knowledge about the effects of the additive manufacturing process, material parameters, and part geometry on printability and combustion efficiency. The work encompasses several disciplines including combustion, fluid dynamics, computational sciences, material science, controls, and propulsion. The outcomes from this research directly relate to the aerospace, aeronautic, and defense industries with additional benefits for similar materials and processes used in the automotive, chemical, energy, and healthcare sectors. The project also incorporates an engineering education component involving outreach to middle school students and integration of research outcomes into undergraduate coursework.Additive manufacturing provides a means to create complex grain geometries not possible with current conventional manufacturing methods, which typically involve a casting process. Producing propellants through additive manufacturing offers several advantages including the ability to create helical ports, center perforations with internal size and shape variations, different materials, and embedded components. With these advantages come performance improvements such as increased combustion efficiency, improved regression rates, and better controllability. The limiting factors for additive manufacturing of these energetic materials are knowledge gaps in governing parameters for optimal performance and manufacture such as viscous parameters for slurry or binder transfer, interlayer bonding, layer/surface roughness, sedimentation during material transfer, layer composition, resolution, and void defects. This award supports the development of mathematical models for the manufacturing process, grain performance simulations, the experimental apparatus to manufacture grains, and the testing of manufactured grains. This work will test the hypothesis that a formulation of parameters – viscosity for slurry or binder transfer, layer/surface roughness, resolution, and sedimentation – can be achieved to obtain optimized propellant efficiency of motors constructed using additive manufacturing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.